The invention relates to artificial turf construction and methods, and, more particularly, to an artificial sports turf which is easy to install and simulates the action of natural playing turf by providing proper shock absorption, improved stability, and reduced turf deflection and irregularities.
With increased leisure time, artificial turf systems for indoor and/or outdoor sports surfaces such as golf greens, golf tee pads, playing fields, golf cart paths and walkways, and other sports surfaces have become more widely used and needed. Natural golf greens typically include a sand base of about 18" in which natural grass grows. The grass is cut to a height of about 1/8-3/16 of an inch to provide a proper playing surface. The sand provides the proper cushioning and drainage, and the grass root system stabilizes the sand.
Previously, various constructions have been provided for artificial turf. For example, U.S. Pat. No. 3,795,180 discloses an artificial surface for a ballfield, patio, and the like which utilizes a plastic extruded net for drainage. U.S. Pat. No. 4,913,596 discloses a composite structure for an athletic field having a series of drain tiles covered with pea gravel which overlay a subgrade which includes a ditch for drainage. U.S. Pat. No. 4,462,184 discloses a system for improving synthetic surfaces such as artificial turf and rubberized asphalt which includes a base drainage system. U.S. Pat. Nos. 5,823,711, 5,752,784, and 5,064,308 disclose various drainage systems for athletic fields and the like.
While the above systems and structures may be suitable for their intended applications, the prior art has not provided a suitable composite structure for an artificial turf surface with low impact properties so that excessive deflections of the surface do not occur, and suitable drainage to remove water from the surface is provided. With increased demand, artificial golf turf is needed which can be easily installed and maintained.
Typically artificial golf course turf has been provided by laying artificial grass on a proper base wherein the grass has a pile range of 3/4"-2 filled with sand so that about 1/8+L to 3/16+L inches of the grass tips are exposed. This closely simulates a natural grass golf green which is typically maintained at about 1/8+L ". Thus, the artificial green has a softness, deflection, and stability which provides a playing action much like a natural grass surface. In the past, crushed stone bases or concrete bases have been used below the artificial turf. However, this type of artificial construction requires installation by professional installers so that the construction and installation techniques have not been suitable for ordinary or less skilled workers to perform. Several different construction problems need to be considered if artificial golf surfaces are to be constructed using ordinary workers and lay persons as is necessary to meet the increased needs for artificial golf courses.
Basically there have been two types of artificial turf systems used in the golf industry or the sporting industry; a polypropylene fiber system and a nylon fiber system, each having different characteristics for play and, primarily, for durability. The polypropylene grasses have been used primarily as soft, shock absorbent putting greens by sweeping a specialized top dressing blend of sand into the fibers to provide the softness of the green. However, the specification has to be followed very closely in order to provide the required softness. By using a specification of an extended pile height of turf grasses, up to approximately 2", filled with sand, the desired softness that is needed can be provided. However, the problem occurs that the turf has to be filled with the sand until the actual finished turf tips are achieved. The top dressing procedure of the polypropylene grass is labor intensive, and about two to five days are required, depending on size, to construct the green using a very intensive top dressing technique which includes adding the sand gently while the fibers are brushed upright as the sand is added. Many sequential, repetitive steps of adding a light sand layer to the grass and brushing the sand are required in order to achieve the proper fill, taking considerable time, effort, and expertise.
It has not been possible to use short pile turf grasses successfully because of the firmness resulting from their short pile. Different pad arrangements have been tried underneath the short pile turfs, such as rubber, foam pads, and geotextile materials, but these arrangements have not been found to provide the shock absorbing resilience needed, and the specifications and techniques required do not lend themselves to construction by lay persons or ordinary construction workers. In order to meet the demands for artificial sports turfs, it must be possible to use lay persons to construct the turf across the country without undue supervision.
To allow someone with less experience to construct artificial turf, local, easily accessible materials, such as sand, need to be utilized in the construction. However, a particular need arises when trying to make a sporting surface base structure or, in this case, a putting green system with loose sand particles in order to keep them stable and firm. Footprints in the surface, or other soft spots would create an imperfect golf ball roll.
Accordingly, an object of the present invention is to provide a composite artificial turf structure which is simple to construct and install yet has the proper softness or shock absorption properties to simulate a natural golf green.
Another object of the present invention is to provide an artificial sports turf which does not have to be installed according to detailed, precise specifications, but may be installed by lay personnel.
Another object of the present invention is to provide an improved artificial turf structure for sports turf having increased drainage for water removal and low impact flexibility that decreases deflection of the surface to provide a natural playing action.
Yet another object of the invention is to provide a base locking grid system which provides stability for subbase construction of artificial turf systems for artificial turf and the like where stability, softness and ease of installation is important.